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Nanoscale relationships between uranium and carbonaceous material in alteration halos around unconformity-related uranium deposits of the Kiggavik camp, Paleoproterozoic Thelon Basin, Nunavut, Canada

By Thomas Riegler, Marie-France Beaufort, Thierry Allard, Anne-Catherine Pierson-Wickmann and Daniel Beaufort

Abstract

International audienceConcentrations of 7% U and 1% Cu were identified in massive, brecciated, and amorphous carbonaceous materials (CM) characterized by strongly negative values of carbon stable isotopes (δ13C = − 39.1‰ relative to PDB). The anomalies are restricted to clay alteration halos developed in Neoarchean Woodburn Lake group metagreywacke that is the predominant host of unconformity-related uranium (U) deposits in the Kiggavik exploration camp. Petrographic and microstructural analyses by SEM, X-Ray Diffraction, HR-TEM and RAMAN spectroscopy identified carbon veils, best described as graphene-like carbon, upon which nano-scale uraninite crystals are distributed. CM are common in U systems such as the classic Cretaceous roll-front deposits and the world-class Paleoproterozoic unconformity-related deposits. However, the unusual spatial and textural association of U minerals and CM described herein raises questions on mechanisms that may have been responsible for the precipitation of the CM followed by crystallization of U oxides on its surfaces. Based on the characteristics presented herein, the CMs at Kiggavik are interpreted as hydrothermal in origin. Furthermore, the nanoscale organization and properties of these graphene-like layers that host U oxide crystallites clearly localized U oxide nucleation and growth

Topics: Hydrothermal, Proterozoic, Carbonaceous material (CM), Unconformity uranium (U) deposits, [ SDU.STU.GC ] Sciences of the Universe [physics]/Earth Sciences/Geochemistry
Publisher: Elsevier
Year: 2016
DOI identifier: 10.1016/j.oregeorev.2016.04.018
OAI identifier: oai:HAL:insu-01312853v1
Provided by: Hal-Diderot

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